This invention relates generally to laser catheters and more particularly, to an expandable laser catheter for removing obstructions from body passages.
Atherosclerotic plaque is known to build up on the walls of arteries in the human body. Such plaque build-up restricts circulation and often causes cardiovascular problems, especially when the build-up occurs in coronary arteries. Other body passages such as the esophagus, ureter and bile ducts, for example, are subject to blockage by tumorous tissue. Accordingly, it is desirable to remove or otherwise reduce plaque build-up and other tissue obstructions from such body passages.
Known catheters use laser energy to remove plaque build-up on artery walls. One such known catheter has a laser source and a catheter body. The catheter body has a proximal end and a distal end, or head, and multiple optical fibers extending between the proximal and distal ends. The laser source is coupled to the optical fibers at the proximal end of the catheter body and is configured to transmit laser energy through the optical fibers.
To remove an obstruction from a body passage, such as atherosclerotic plaque in an artery, the catheter is positioned in the artery so that the distal end of the catheter is adjacent to the plaque. The laser source is then energized so that laser energy travels through the optical fibers and photoablates the plaque adjacent the distal end of the catheter. The catheter is then advanced further through the artery to photoablate the next region of plaque build-up.
While known laser catheters are generally acceptable for removing small obstructions, such catheters are limited to opening a path the size of the catheter head on each pass through the body passage. The multiple passes which are required for removing larger areas of obstruction increase the possibility of damaging the passage inner wall. In addition, multiple passes increase the possibility that a piece of the obstruction will break free, enter the blood stream and result in vessel blockage. Other known laser catheters are limited by the relative inflexibility of the catheter distal end which may inflict damage to body passage inner walls as the catheter is advanced.
Accordingly it would be desirable to provide a laser catheter which can remove substantial portions of an obstruction in a single pass. It would also be desirable to provide a laser catheter having a flexible, adjustable distal end which can substantially conform to the inner dimensions of the body passageway to minimize damage to the inner wall. It would be further desirable to provide a laser catheter which can expand and contract during photoablation to increase the area of obstruction which may be photoablated in a single pass through a body passage.
These and other objects may be attained by a laser catheter which, in one embodiment, includes a shaftway having a proximal end and a distal end including a flexible portion. The flexible portion is fabricated from a pliable material and is configured in folds which are radially oriented about the longitudinal axis of the catheter. The flexible portion is configured to be expanded by, for example, an inflatable balloon which is attached within the flexible portion. Optical fibers extend along the length of the catheter to transmit laser energy from the proximal end to the distal end of the catheter, and are attached to the catheter at the distal end. The ends of the optical fibers, at their attachments to the distal end, are directed toward targeted regions of an obstruction.
In use, a guidewire is inserted into a body passage such as an artery and advanced past the obstruction. The catheter is then advanced over the guidewire through the artery until the distal end of the catheter is adjacent to the obstruction, such as atherosclerotic plaque. The balloon is then inflated to expand the flexible portion of the distal end. Upon expansion, the flexible portion substantially conforms to the inner dimensions of the body passage and is enlarged so that the flexible portion can hold a core of material from the obstruction. A laser connected to the optical fibers at the catheter proximal end is then energized, and the laser energy transmitted through the optical fibers photoablates the obstruction in the regions targeted by the optical fibers. The catheter is then advanced and the process repeated.
As the catheter is advanced and targeted regions photoablated, the catheter detaches a separate core of material from the obstruction. As the core is formed the catheter advances over the core so that ultimately the core is completely contained within the flexible portion. To remove the core of the obstruction, the balloon is deflated and the flexible portion contracts and holds the core of the obstruction. The catheter is then withdrawn from the body passage to remove the core of the obstruction from the body passage.
In an alternative embodiment, the laser catheter utilizes mechanical spring force to expand the distal end of the laser catheter. In this alternative embodiment, the optical fibers are attached to a stiff shaftway. A fin structure including a plurality of fins fabricated from a spring material is attached to the distal end of the shaftway. The stiff shaftway is capable of transmitting torque to the distal end so that the fin structure can be rotated, thus facilitating advancement of the fin structure, and complete removal of the obstruction. The fins have a substantially rolled shape and are expandable from a retracted position to an extended position. In both the retracted position and the extended position the fins retain a substantially rolled shape which substantially conforms to the inner dimensions of the body passage, to minimize damage to the inner wall of the body passage. At the fin structure the ends of the optical fibers are attached and spread across the fins and are directed parallel to the shaftway. The laser catheter further includes an outer catheter body or sheath slidably disposed over the shaftway to retain the fin structure in the retracted position.
In use of the alternative embodiment, a guide wire is introduced into a body passage and advanced past the obstruction. The laser catheter is introduced over the guide wire and advanced toward the obstruction. When the distal end of the catheter is adjacent the obstruction, the shaftway is rotated and advanced so that the fin structure is pushed out of the outer catheter body, thus releasing the fins from the retracted position and allowing them to expand to the extended position. In the extended position, the fins contact the passage inner wall and the ends of the optical fibers are directed parallel to the inner wall of the passage. The fin structure can be further advanced along the passage wall by advancing the shaftway and sliding the fin structure along the passage wall. Laser energy is used to photoablate regions of the obstruction targeted by the optical fibers. The mounting of the optical fibers on the fin structure allows the obstruction to be removed from around the passage central axis (around the guide wire) to the outside diameter of the passage, with the fins protecting normal passage inner wall from photoablation. When the obstruction has been removed, the fin structure is rotated and pulled back into the outer catheter body, thus causing the fins to retract to the retracted position. The catheter is then removed from the body passage.
In additional alternative embodiments especially useful for opening in-stentrestenosis, laser energy may be directed radially outward from the shaftway instead of parallel to the shaftway. This may be accomplished by attaching the ends of the optical fibers at the fin structure so that the ends of the fibers are directed radially outward from the shaftway, or alternatively, by coupling prisms to the ends of the optical fibers at the fin structure to direct laser energy radially outwards from the shaftway.
The above described laser catheter removes substantial portions of an obstruction in a single pass by expanding the distal end of the catheter to substantially conform to the inner dimensions of the body passage. The laser catheter further minimizes damage to the body passage inner wall with a flexible, adjustable distal end. Further, the laser catheter may be expanded and contracted during photoablation to increase the area of obstruction which may be photoablated in a single pass. By removing substantial portions of an obstruction in a single pass, the laser catheter obviates the need for multiple and potentially damaging passes through the body passage.